1. Atlantic Bluefin Tuna (Thunnus thynnus)

Atlantic bluefin tuna are large, streamlined fish that live in the pelagic zone. Tuna are a popular sportfish due to their popularity as a choice for sushi, sashimi and steaks. Consequently, they have been heavily overfished.. Bluefin tuna are long-lived animals. It is estimated that they can live up to 20 years.

Bluefin tuna are bluish-black on their dorsal side with a silvery coloration on their ventral side. They are a large fish, growing to lengths of 9 feet and weights of 1,500 pounds.

2. Southern Bluefin (Thunnus maccoyii)

The Southern bluefin tuna, like the Atlantic bluefin tuna, is a fast, streamlined species. The Southern bluefin is found throughout the oceans in the Southern Hemisphere, in latitudes roughly from 30-50 degrees south. This fish can reach lengths up to 14 feet and weights up to 2,000 pounds. Like other bluefin, this species has been heavily overfished.

3. Albacore Tuna/Longfin Tuna (Thunnus alalunga)

Albacore are found throughout the Atlantic Ocean, Pacific Ocean and Mediterranean Sea. Their maximum size is about 4 feet and 88 pounds. Albacore have a dark blue upper side and silvery white underside. Their most distinctive characteristic is their extremely long pectoral fin.

Albacore tuna is sold commonly as canned tuna and may be called "white" tuna. There are advisories about consuming too much tuna because of high mercury levels in the fish.

Albacore are sometimes caught by trollers, who tow a series of jigs, or lures, slowly behind a vessel. This type of fishing is more eco-friendly than the other method of capture,longlines, which can have a significant amount of bycatch..

4. Yellowfin Tuna (Thunnus albacares)

The yellowfin tuna is a species you'll find in canned tuna, and may be called Chunk Light tuna. These tuna are often caught in a purse seine net, which faced an outcry in the U.S. for its effects on dolphins , which are often associated with schools of tuna, and were therefore captured along with the tuna, causing the deaths of hundreds of thousands of dolphins each year. Recent improvements in the fishery have reduced the dolphin bycatch.

The yellowfin tuna often has a yellow stripe on its side, and its second dorsal fins and anal fins are long and yellow. Their maximum length is 7.8 feet and weight is 440 pounds. Yellowfin tuna prefer warmer, tropical to subtropical waters. This fish has a relatively short lifespan of 6-7 years.

5. Bigeye Tuna (Thunnus obesus)

The bigeye tuna looks similar to the yellowfin tuna, but has larger eyes, which is how it got its name. This tuna is usually found in warmer tropical and subtropical waters in the Atlantic, Pacific and Indian Oceans. Bigeye tuna can grow up to about 6 feet in length and weigh up to about 400 pounds. Like other tunas, the bigeye has been subject to overfishing.

6. Skipjack Tuna/Bonito(Katsuwonus pelamis)

Skipjacks are a smaller tuna that grow to about 3 feet and weigh up to about 41 pounds. They are a wide-ranging fish, living in tropical, subtropical and temperate oceans around the world. Skipjack tunas have a tendency to school under floating objects, such as debris in the water, marine mammals or other drifting objects. They are distinctive among tunas in having 4-6 stripes that run the length of their body from gills to tail.

7. Little Tunny (Euthynnus alletteratus)

The little tunny is also known as the mackerel tuna, little tuna, bonito and false albacore. It is found worldwide in tropical to temperate waters. The little tunny has a large dorsal fin with high spines, and smaller second dorsal and anal fins. On its back, the little tunny has a steel blue coloration with dark wavy lines. It has a white belly. The little tunny grows to about 4 feet in length and weighs up to about 35 pounds. The little tunny is a popular gamefish and is caught commercially in many locations, including the West Indies.